Segment Information - Schedule of Segment Revenues, Depreciation and Amortization, and Operating (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Segment Reporting Information [Line Items]
Total revenues	$ 202.0	$ 184.1	$ 541.3	$ 532.4
Depreciation & amortization:
Total depreciation and amortization	6.2	5.7	18.5	16.8
Operating income from continuing operations:
Total operating income from continuing operations	12.7	11.5	20.3	28.7
Corporate activities
Operating income from continuing operations:
Total operating income from continuing operations	(5.1)	(2.9)	(16.0)	(10.1)
Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues	148.5	138.4	403.8	409.3
Depreciation & amortization:
Total depreciation and amortization	4.5	4.5	13.6	13.2
Kratos Government Solutions | Reportable Segments
Operating income from continuing operations:
Total operating income from continuing operations	14.1	11.1	31.1	33.2
Unmanned Systems
Segment Reporting Information [Line Items]
Total revenues	53.5	45.7	137.5	123.1
Depreciation & amortization:
Total depreciation and amortization	1.7	1.2	4.9	3.6
Unmanned Systems | Reportable Segments
Operating income from continuing operations:
Total operating income from continuing operations	3.7	3.3	5.2	5.6
Service revenues
Segment Reporting Information [Line Items]
Total revenues	67.6	70.8	194.1	207.1
Service revenues | Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues	67.6	70.8	194.1	207.1
Product sales
Segment Reporting Information [Line Items]
Total revenues	134.4	113.3	347.2	325.3
Product sales | Kratos Government Solutions
Segment Reporting Information [Line Items]
Total revenues	$ 80.9	$ 67.6	$ 209.7	$ 202.2